In display panels such as PANAPLEX panels used in the prior art, mercury is provided in the gas atmosphere to minimize cathode sputtering, and the mercury is provided either in a capsule mounted in the panel tubulation, or it is provided in a metal capsule disposed at an end of the panel within the envelope. Both arrangements work well, but they are unsatisfactory because the capsules which are required are relatively expensive.
The present invention permits the utilization of an inexpensive mercury capsule and a barrier support therefor which can be formed simply and inexpensively.